System and method for using timing data from an incomplete packet to more accurately determine the position of a transmitter

Abstract

A system and method for using timing data from an incomplete packet to more accurately determine the position of a transmitter in a workspace is provided. A radio signal packet comprising a header portion containing timing data, and a data portion, is transmitted from a transmitter. Upon successful receipt by at least one receiver in a known location, header portions from incomplete receptions at other receivers are correlated to the transmission. Timing data from the correlated, and incomplete, receptions are then used by a location determining algorithm to improve position accuracy and extend the range of the system.

I/We claim: 
     
         1 . A method for using timing data from an incomplete packet to more accurately determine the position of a transmitter in a workspace comprising the steps of:
 a. transmitting a radio signal packet from said transmitter, said packet comprising a header portion which includes timing data and a data portion which includes data and tag identification information;   b. receiving said header portion and said data portion of said radio signal packet at a first receiver positioned in a known location within a first zone of the workspace, said first zone being defined by a radius from the transmitter where both the header portion and data portion of the radio signal packet are received;   c. receiving said header portion but not said data portion of said radio signal packet at a second receiver positioned in a known location within a second zone of the workspace, said second zone being defined by a first boundary associated with an outer boundary of the first zone and a second boundary defined by a radius from the transmitter where the header portion but not the data portion of the radio signal packet are received;   d. transmitting at least the timing data from the header portion of the radio signal packet at the first receiver to a server;   e. transmitting at least the timing data from the header portion of the radio signal packet at the second receiver to the server;   f. implementing a location determining algorithm using the timing data from the header portion of the radio signal from the first receiver and the timing data from the header portion of the radio signal from the second receiver to determine the location of the transmitter in the workspace.   
     
     
         2 . The method of  claim 1  further comprising the steps of:
 a. identifying the transmitter associated with the radio signal packet at the first receiver by the tag identification data from the data portion of the packet; 
 b. identifying the transmitter associated with the radio signal packet at the second receiver by comparing a time of arrival of the radio signal packet at first receiver to a time of arrival of the radio signal packet at the second receiver, and, if the time of arrival at the second receiver is within a certain range of the time of arrival at the first receiver, assigning tag identification data at the second receiver to match the tag identification data at the first receiver. 
 
     
     
         3 . The method of  claim 2  wherein the certain range of timing data is +/−10 microseconds. 
     
     
         4 . The method of  claim 2  further comprising the step of substituting the data portion of the packet from the radio signal packet at the first receiver for the missing data portion of the packet from the radio signal packet at the second receiver if the time of arrival at the second receiver is within the certain range of the time of arrival at the first receiver. 
     
     
         5 . The method of  claim 2  wherein the steps of receiving and transmitting are performed at a plurality of first receivers and a plurality of second receivers, and further comprising the step of combining the data portions of the packets from the radio signal packets at each of the first receivers into a single data set for all receivers. 
     
     
         6 . The method of  claim 1  wherein there are a plurality of transmitters that transmit at different times and further comprising the step of differentiating signals from each transmitter relative to the other transmitters. 
     
     
         7 . The method of  claim 1  wherein the steps of receiving and transmitting are performed at a plurality of first receivers and a plurality of second receivers. 
     
     
         8 . The method of  claim 7  wherein there are a plurality of transmitters located remotely from one another that transmit at the same time, and further comprising the step of spatial disambiguation to differentiate each transmitter from the other remote transmitters. 
     
     
         9 . The method of  claim 8  wherein only packets received at receivers that are located in only one of the zones defined around plurality of transmitters are considered. 
     
     
         10 . The method of  claim 6  wherein transmissions from each one of said plurality of transmitters occur at known regularly scheduled transmission times and further comprising the steps of:
 a. comparing the timing information from the header portion of the radio signal packet at each receiver within the first zone and second zone with the known transmission times for each transmitter; and 
 b. correlating the timing information from the header portion of the radio signal packet at each receiver within the first zone and second zone with the known transmission times for each transmitter to determine from which of the plurality of transmitters the radio signal packet was transmitted. 
 
     
     
         11 . A system for using timing data from an incomplete packet to more accurately determine the position of a transmitter comprising:
 a. a radio signal packet transmitted from said transmitter, said packet comprising a header portion which includes timing data and a data portion which includes data and tag identification information;   b. a first receiver positioned in a known location within a first zone of the workspace, said first zone being defined by a radius from the transmitter where both the header portion and data portion of the radio signal packet are received;   c. a second receiver positioned in a known location within a second zone of the workspace, said second zone being defined by a first boundary associated with an outer boundary of the first zone and a second boundary defined by a radius from the transmitter where the header portion but not the data portion of the radio signal packet are received;   d. a server for receiving and processing at least the timing data from the header portion of the radio signal packet at the first receiver, and at least the timing data from the header portion of the radio signal packet at the second receiver;   e. a location determining algorithm using the timing data from the header portion of the radio signal from the first receiver and the timing data from the header portion of the radio signal from the second receiver, said algorithm implemented to determine the location of the transmitter in the workspace.   
     
     
         12 . The system of  claim 11  further comprising:
 a. means for identifying the transmitter associated with the radio signal packet at the first receiver by the tag identification data from the data portion of the packet; 
 b. means for identifying the transmitter associated with the radio signal packet at the second receiver by comparing a time of arrival of the radio signal packet at first receiver to a time of arrival of the radio signal packet at the second receiver, and, if the time of arrival at the second receiver is within a certain range of the time of arrival at the first receiver, assigning tag identification data at the second receiver to match the tag identification data at the first receiver. 
 
     
     
         13 . The system of  claim 12  further comprising means for substituting the data portion of the packet from the radio signal packet at the first receiver for the missing data portion of the packet from the radio signal packet at the second receiver if the time of arrival at the second receiver is within the certain range of the time of arrival at the first receiver. 
     
     
         14 . The system of  claim 10  wherein there are a plurality of transmitters that transmit at different times and further comprising means for differentiating signals from each transmitter relative to the other transmitters. 
     
     
         15 . The system of  claim 10  wherein there are a plurality of transmitters located remotely from one another that transmit at the same time, and further comprising spatial disambiguation means to differentiate each transmitter from the other remote transmitters.